Or if you are a dev with write access (and don't want to use your own github repo as well) use:

git clone -o github git@github.com:paparazzi/paparazzi3.git

The option -o <name> uses name to keep track of the upstream repository instead of using the remote name origin. It is recommended to call the remote for the papaprazzi master repo github and name your own github remote according to your name to avoid confusion.

Adding remotes

Assuming for example that you forked the paparazzi master repo directly on github and cloned from your own github repo as explained by the first option above you want to add the master repo as a remote with the name github: